Arduino CNC Shield Power Routing

[Desertboy]

The problem with CNC machining, is it usually requires far faster and more accurate motion than 3D printing, and an Arduino is not really up to the task.
Even an ARM processor isn't ideal, as getting jitter free motion needs good clock scaling, which can be handled far better in an FPGA, which is why you'll find nearly all CNC motion controllers use an FPGA for motion generation, often paired with some form of microprocessor which handles communication and the maths for generating the motion paths, before passing the required motion to the FPGA.
LinuxCNC and Mach running via a parallel port also have the same issue, however they ultimately rely on using a sledgehammer to crack a nut, by throwing enough processing power at the problem, you can get it to work well enough it's not a problem.

And then you have the available hardware. Nearly all shields I'm sure have been designed with 3D printing in mind, where speed and acceleration requirements aren't that great, so 24V is acceptable. If you were to use those same speeds on any reasonably sized router or mill, it would be painfully slow.
Hardware really is a case of, you get what you pay for.

The CNCshield is designed for grbl which is cnc router firmware not 3d printing! It can pass up to 36v to steppers (It's designed for a hobby machine after all) but if you need 60v to the drivers you can do that easily as well. Most people use cheap ass Polou steppers which are not suitable for 36v but you can get a lsightly more expensive driver than will push 36v fine or wire a real driver to replace the cheap chip drivers the cncshield is designed to take on board.

Of course it's not as good as much more expensive solutions but it's very powerful for the price (£25 including 4 stepper drivers!) and not as useless as you might think but I will move to a breakout board solution relatively soon I consider it the least essential purchase right now in getting the thing built and cutting.

Ardunio and cncshield are also very good for testing nema's so when I do upgrade I will have a simple test bed for the recovered motor's I collect.

grbl is very stable these days, maybe not the quickest of course but they are rock solid stable.

"The controller is written in highly optimized C utilizing every clever feature of the AVR-chips to achieve precise timing and asynchronous operation. It is able to maintain up to 30kHz of stable, jitter free control pulses."

[m_c]

The CNCshield is designed for grbl which is cnc router firmware not 3d printing! It can pass up to 36v to steppers (It's designed for a hobby machine after all) but if you need 60v to the drivers you can do that easily as well. Most people use cheap ass Polou steppers which are not suitable for 36v but you can get a lsightly more expensive driver than will push 36v fine or wire a real driver to replace the cheap chip drivers the cncshield is designed to take on board.

That CNC shield is just a glorified header board, with pinouts optimised for grbl. You could just as easily use it for 3D printing.
Regardless, what I was highlighting was the more stringent requirements for CNC.

Of course it's not as good as much more expensive solutions but it's very powerful for the price (£25 including 4 stepper drivers!) and not as useless as you might think but I will move to a breakout board solution relatively soon I consider it the least essential purchase right now in getting the thing built and cutting.

Ardunio and cncshield are also very good for testing nema's so when I do upgrade I will have a simple test bed for the recovered motor's I collect.

Just for clarity, I never said an Arduino is not a useable option, it's just not an ideal one.

grbl is very stable these days, maybe not the quickest of course but they are rock solid stable.

"The controller is written in highly optimized C utilizing every clever feature of the AVR-chips to achieve precise timing and asynchronous operation. It is able to maintain up to 30kHz of stable, jitter free control pulses."

And if you have a look at the grbl source, you'll see it's using a similar smoothing algorithm to Repetier (which incidentally has a nice explanation on how it works). It may be jitter free, but in order to achieve the jitter free, you have to compromise accuracy. And then to achieve the higher pulse rates, it starts scaling steps, so you loose even more accuracy, and introduce a certain amount of jitter.

If I didn't have as much work to do just now, I'd try connecting an arduino to a datalogger, and see just how jitter free the output really is.

P.S. the technobabble may impress your average arduino coder, but all they're ultimately doing is handling pulse generation in native AVR C, and relying on ISRs for timing. The only thing optimised other than good coding technique, is avoiding using C++ and the arduino compiler, which is inherently bloated.

[AcrimoniousMirth]

That CNC shield is just a glorified header board, with pinouts optimised for grbl. You could just as easily use it for 3D printing.
Regardless, what I was highlighting was the more stringent requirements for CNC.

True that! But you wouldn't as you'd have to add thermistor control, heated bed, heated nozzle... and to be in line with today's cheapest printer motherboard (the RAMPS) you'd also need to add on extra for servo control, LCD and SD integration etc.
If you had one already it'd be interesting turning it into a printer driver but you wouldn't purchase one for printing, especially as said RAMPS is about £18 including the necessary drivers and LCD/SD :)

[AcrimoniousMirth]

The CNCshield is designed for grbl which is cnc router firmware not 3d printing! It can pass up to 36v to steppers (It's designed for a hobby machine after all) but if you need 60v to the drivers you can do that easily as well. Most people use cheap ass Polou steppers which are not suitable for 36v but you can get a lsightly more expensive driver than will push 36v fine or wire a real driver to replace the cheap chip drivers the cncshield is designed to take on board.

Of course it's not as good as much more expensive solutions but it's very powerful for the price (£25 including 4 stepper drivers!) and not as useless as you might think but I will move to a breakout board solution relatively soon I consider it the least essential purchase right now in getting the thing built and cutting.

Ardunio and cncshield are also very good for testing nema's so when I do upgrade I will have a simple test bed for the recovered motor's I collect.

grbl is very stable these days, maybe not the quickest of course but they are rock solid stable.

"The controller is written in highly optimized C utilizing every clever feature of the AVR-chips to achieve precise timing and asynchronous operation. It is able to maintain up to 30kHz of stable, jitter free control pulses."

Well said! I'd like to add that it's even cheaper than £25 now! CNC shield and Arduino UNO coming to about £10-15 total now including the cheap pololus.
I knew I'd be using NEMA23s (part of the limitation of me recycling old bits) so I reused some old DRV8825 drivers which as you say are capable of 24-36V and higher currents, so are suitable for the NEMA23s. Those back in the day would've cost me about £7 so you're right, cheap as dirt for hobbyists :)

[Desertboy]

Well said! I'd like to add that it's even cheaper than £25 now! CNC shield and Arduino UNO coming to about £10-15 total now including the cheap pololus.
I knew I'd be using NEMA23s (part of the limitation of me recycling old bits) so I reused some old DRV8825 drivers which as you say are capable of 24-36V and higher currents, so are suitable for the NEMA23s. Those back in the day would've cost me about £7 so you're right, cheap as dirt for hobbyists :)

I'm going to buy 4 AM882H and a 60v power supply when I finish my build but at moment finishing the Z axis and mounts seem to be more important.

But now you can buy 5*DRV8825 for £7 from china delivered which is crazy.